Rubbing machine



March 4, 1958 R. .1. CHQAMPAYNE 2,825,188

RUBBING MACHINE 5 SheetsSheet 1 Filed March 19, 1953 QQE; ch41 pqlsvge W, wmiw R. J. CHAMPAYNE 2,825,188

March 4, 1958 RUBBINQ MACHINE 5 Sheets-Sheet 4 Filed March 19, 1953 m algae, I $14- w cAt'r-rnnMB Unite This invention relates to a portable rubbing machine of the reciprocating type having a single rubbing shoe or pad, and the general object to provide a new and improved rubbing machine of this character which is simple and inexpensive in construction, durable and vibrationless in operation, and of optimum over-all dimensions.

Another object is to provide a single shoe reciprocating sander having a weight for counterbalancing the rubbing shoe mounted in an out of the way position above the shoe and reciprocated in synchronism with the latter.

A further object is to support the rubbing shoe and counterweight closely adjacent each other and for endwise reciprocation without the use of machined guideways or complicated bearings.

A more detailed object is to provide a single counterweight lying adjacent and about the rubbing shoe and to reciprocate the weight and shoe in opposite directions through the intermediary of upright levers fulcrumed intermediate their ends and each pivotally connected at opposite ends to the shoe and weight respectively.

Still another object is to provide a portable rubbing machine in which the shoe driving motor is started and stopped in response to the application and release of downward pressure on the part of the motorcasing by which the machine is gripped and moved about a work surface.

A further object is to provide for reciprocation of the taken in connection with the accompanying drawings, in

which v Figure 1 is a perspective view of the preferred form of rubbing machine embodying the novel features of the present invention. g p

Fig; 2 is a perspective view of the counterweight and its support. Fig. 3 is a longitudinal central sectional view taken substantially along the line 3-3 of Fig. 6. f Fig. .4 is a fragmentary section taken along the line 44 of Fig. 3.

Fig; 5 is a perspective view ofthe rubbing shoe and its support. I

'Fig. 6 is a section taken substantially along the line 66 of Fig. 3.

Fig. 7 is a fiuidcircuit diagram. Fig. 8 is a view similar to Fig. 3 showing a modification. Fig. 9isa perspective bottom view of a connecting rod shown in Fig. 8.

States PatentO Patented Mar. 4, 1958 flce Fig. 10 is a fragmentary longitudinal sectional view of the connecting rod and the associated crank.

Figs. 11 and 12 are longitudinal and transverse sectional views similar to Figs. 3 and 6 showing another modified form of the invention.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and will herein describe in detail the preferred embodiments. do not intend to limit the invention by such disclosure, but aim to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the'appended claims.

In the preferred form. shown in Figs. 1 to 7 of the drawings, the invention is incorporated in a portable type rubbing machine comprising generally a rigid body ltl housing a power driven motor 11 for reciprocating a single rubbing shoe 12 disposed below the body and supported by the latter. Herein, the body comprises a relatively square block 13 to whichend plates 14 are attachw ed by screws 15 and a top plate 16 is attached by screws 17. The top plate is rounded as shown in Fig. l to facilitate hand gripping and is cast integral with a skirt 18 depending along the sides of the block and spaced from the end plates 14.

The motor 11 as shown in Fig. 3 is of the reciprocatory type preferably using air as a motivating fluid. It com prises a hollow piston 19-of light metal slidable in a cylinder 20 closed at opposite ends by the plates 14 and extending horizontally through the lower part of the block 13 which is formed with air passages as shown in Fig. 7 terminating in ports 21 and 22 at opposed ends of the cylinder, ports 23 and 24 adjacent but spaced from the cylinder ends, and ports 25 and 26 spaced apart near the center of the cylinder and cooperating with a hole 27 in the side of the piston. Compressed air supplied through a flexible hose 28 and a passage 29 in the body 10 is admitted to the motor under the control of a manually operable valve '30 (Fig. 4) and a distributing valve 31 having a spool 32 reciprocable in a cylinder 33 which extends crosswise of the cylinder in the upper part of the block 13.

In the right hand position of the valve spool shown in Fig. 7, compressed air enters'the valve cylinder at 34 and is directed through a port 35 to the port 22 at the left end of the motor cylinder, the other cylinder end then being open through the port 21, a valve port 36 and an exhaust outlet "37 from the valve cylinder. When the piston 19 in thus moving to the right reaches the position shown in Fig. 7, it uncovers the port 23 to admit pressure fluid through a passage 38 to the right end of the valve cylinder. At the same time, the port 24 is covered but the passage 39 from the other end of the valve cylinder is connected to an exhaust passage through the hollow piston by virtue of the registry of the piston hole' with the port 26. As a result, the spool 32 is shifted to the left end of the cylinder to connect the valve port 36 with the supply port 40 and thus admit compressed air to the right end of the power cylinder, the other end communicating with the exhaust port 37 through the port 35. This condition obtains until the piston 19 uncovers the port 24 whereupon the position of the valve spool is reversed by the admission It is to be understood, however, that I The rubbing shoe 12 comprises a generally rectangular rigid plate secured to a thin plate 51 which in turn is secured to and covered on the bottom by a yieldable pad 52 of sponge rubber or the like against which a sheet 53 of abrasive or other rubbing material may be secured. For this purpose, the end portions of the sheet are bent upwardly and around the ends of the pad and held by suitable friction clamps 54 urged downwardly by spring pressure.

The rubbing shoe is supported by and mounted below the body 10 for endwise reciprocation without the ne cessity of using sliding way surfaces. For this purpose, upright levers 55 are disposed at opposite ends of the body 10 and fulcrumed intermediate their ends. on pins 56.. In the present instance, the pins extend through enlargements 57 at the centers of the levers fitting closely between spaced lugs 58" integral with and projecting outxardly and horizontally from the plates 14. The upper ends of the levers areenlarged and elongated as indicated at 59 and apertured to receive bearing bushings 60 which are mounted in sleeves 61 of rubber or other yieldable material.

Preferably, the rubbing shoe 12 is suspended from the upper ends of the levers 55 through the medium of rigid means by which the thrust on the shoe incident to pressing the pad against the work surface is transmitted directly to the lever fulcrurns 56. To this end, laterally spaced fiat lugs 62 are cast integral with and project upwardly from each end of the shoe plate 50 and straddle the levers 55. The lugs parallel each other and their upper ends are clamped as by screws 63 against the opposite ends of pins 64 journaled in the bearings 60 and projecting far enough beyond the ends of the lever enlargements 59 to permit free pivoting of the shoe on the levers. To impart the desired rigidity to the shoe, the outer edges of the lugs 62 of each pair are joined integrally by a web 65 (Fig. 5) while the lugs on each longi tudinal edge of the shoe are connected rigidly by flanges 66. The shoe plate 50, the lugs 62, and the flanges 65 i and 66 thus form a rigid box-like structure which may, if desired, be die cast from relatively light weight metal.

To minimize vibration of the body 10 during recipro cation of the shoe 12, the latter. is counterbalanced by a weight 67 which is disposed between the shoe and the body 10 and is reciprocated in unison with the shoe but always in the reverse direction. The counterweight is elongated and somewhat shorter and narrower than the shoe 12 so as to be disposed in all positions of the shoe and counterweight within the box-like shoe frame defined by the end and side flanges 65 and 66. Herein, the weight comprises a rigid casting in the form of a channel having relatively thick bottom and upstanding parallel side fiangcs 68 Whose opposite ends straddle enlargements 69 formed on the lower ends of the levers 55 to which the lugs are pivotally connected by pins 70 (Fig. 6) extending through rubber cushions 71 in the enlargements and journaled in bearing bushings 72 supported by the latter with their axes parallelto the upper bushings 60. The counterweight is thus suspended from the lower ends of the levers so as to reciprocate endwise with the rubbing shoe but in the opposite direction.

To reciprocate the shoe 12 and the counterweight:

67 back and forth, the driven element or piston 19 of the motor 11 is extended outwardly from the body or frame 10 and joined to the levers 55. Preferably, the motion is transmitted through the intermediary of the counterweight 67 since it comprises a single rugged and elongated part and is located advantageously below the supporting body 10. Accordingly, the connection comi prises a simple stud'74 pressed into an upwardly opening hole 75 in the center of the counterweight and projecting upwardly through a longitudinally elongated slot 76 in the under side of the cylinder 20.. A substantial length of the stud extends slidably into a bushing 77 surrounded by rubber 73 which is seated in an outwardly opening hole 79 formed in the side of the hollow piston 19. The stud is thus adapted to slide up and down within the bushing as the counterweight rises and falls in traversing its slightly arcuate path.

The counterweight 67 which necessarily is a rugged part is thus utilized to transmit power from the motor to each of the levers 55 each end of the counterweight being placed alternately under tension and compression. As a result, the parts required for transmitting power from the motor to the rubbing shoe may be made of minimum size and weight considering the magnitude and rapid reversal of the forces.

To achieve perfect balance and vibrationless operation of the tool as described above the mass of the counterweight 67 and the reciprocating parts that move therewith including the piston 19 and the stud 74 are made substantially equal to the mass of the rubbing shoe 12 and its associated parts including the box-like frame 65, 66 and the sheet clamps 54. These parts are so constructed that the centers of gravity of the two oppositely reciprocating masses are disposed in a common plane a close to the top of the shoe 12. Such advantageous location of the centers of mass is made possible by suspending the shoe from the upper ends of the levers 55 which involves the use of the upstanding frame 65, 66 and therefore raising of the center of mass of the shoe to a plane far enough above the top of the shoe proper to permit the location of the counterbalancing mass in the same plane.

Preferably, the stroke of the piston 19 and therefore the range of reciprocation of the shoe is about 7 of an inch and the motion transmitting connections above described are arranged to swing the levers 55 through angles I) (Fig. 3) of about 20 degrees which angles are bisected by vertical planes through the fulcrums 56. With this arrangement, each point on the shoe describes a very shallow arcuate path which, due to the suspension of the shoe from the upper ends of the levers 55, curves downwardly at opposite ends. Owing to the length of the lever arms and the small angle through which they are oscillated, the foreshortening of the arc traversed by the shoe 12 is only a few thousandths of an inch. The fact that the shoe motion thus deviates slightly from a true rectilinear path is of no consequence insofar as the cutting etficiency of the abrasive is concerned, especially because of the yieldable character of its backing 52.

Since the opposite ends of the counterweight 67 are suspended from the lower ends of the levers 55, each part of the weight moves in an arcuate path of the samelength and shape as the shoe path but inverted relative to the latter. Thus, the vertical components of the shoe and counterweight motions due to their slightly arcuate paths of travel are always opposed to each other so that they neutralize each other. There are therefore no forces tending to cause the tool to bounce relative to the work surface. Moreover, it has been found that the cutting efiiciency of the abrasive is improved when the opposite ends of the slightly arcuate shoe path are curved downwardly as described above due to suspension of the shoe from the upper ends of the levers 55..

Also, it will be observed that the counterweight is disposed in an out-of-the-way position between the rubbing shoe and the supporting body 10 and, while the weight and shoe move in opposite directions and the strokeof the counterweight is preferably though not necessarily equal to that of the shoe, there is no danger of interference between the two and no projection of any part of the weight outwardly beyond the ends of the shoe in any position of the latter.

To facilitate control of the motor 11 by the hand of the operator which is gripping the upper part 16 of the body 10 to hold the tool and move the same across the Work surface, provision may be made for actuating the control valve 30 from an elongated and somewhat flattened leverarm 80 pivoted at 81 on one end of the body 10 and projecting forwardly substantially to the other end.v The angles on opposite sides of the vertical.

arm bears downwardly on the upper end of the stem 82 of the valve 30 and its free end is movable up and down in a recess 83 formed in the top casting of the body. When the operator is gripping the sides of the skirt 16 to support the tool, he may, by manipulating his hand, lower the arm 80 to the position indicated in phantom in Fig. 3 thereby opening the valve 30. The latter will close automatically when the pressure on the arm is relieved.

The form of the invention illustrated in Figs. 8, 9, and is identical with that described above except for the fact that the motor 11 is of the rotary instead of the reciprocatory type. It may comprise a series of vanes 85 mounted on an eccentric rotor 86 to move around a cylinder 87 within the body 10. The rotor is on a shaft 88 projecting downwardly from the bottom of the body 10 and the rotary motion of the shaft is converted to oscillatory motion of the levers 55 through a 'crank 89 coacting with a connecting rod 90 which is disposed within the counterweight channel and is joined pivotally to one end of at least one of the levers -55. Herein, the connecting rod comprises two plates suitably clamped against the opposite ends of suitable spacers and of the outer race rings 91 of two self-alining'antifriction bearings 92. The inner race ring of one bearing is pressed onto the eccentric 89 while the inner ring of the other bearing is pressed onto a stud 93 pressed into and upstanding from the bottom of the counterweight 67.

It will be seen from the foregoing that during rotation of the motor shaft 88 and the crank 89, the connecting rod 90 will shift the stud 93 back and forth and, through the medium of the counterweight, will rock the levers 55 in unison and through equal ranges extending over equal As before, the counterweight and rubbing shoe are thus reciprocated endwise through equal distances in opposite directions. Owing to the short range of oscillation of the levers 55 and the yieldability of the backing 52, the sheet 53 remains in full rubbing contact with the work surface being operated upon.- The self-alining character of the bearings 92 compensates for the slight variations in angularity between the crank 89 and the stud 93 during the reciprocation of the counterweight.

Instead of connecting the crank 89 to the counterweight 67, the crank motion may, as shown in Figs. 11 and 12, be applied directly to the rubbing shoe and the latter may be suspended from the lower ends of the levers 55. In this case, lugs 95 at opposite ends of a channel 96 riveted to the top of the shoe plate 51 straddle the lower ends 69 of the levers 55 and are clamped against opposite ends of the pivot pins 7%). i The lugs 95 project upwardly through slots 9t in the bottom of the counterweight 67 whose side flanges 97 straddle the upper ends 59 of the levers 55 and are clamped against the pivot pins 64. A

stud 98 (Fig. 11) is rigid with and upstands from the top of the rubbing shoe through a slot 99 in the bottom of the counterweight channel, the upper end of the stud being received in the inner race ring at the outer end of the connecting rod 90.

As in the case of the arrangement shownin Fig. 8, the rotary motion of the shaft 88 is converted into opposite reciprocatory motion of the rubbing shoe and counterweight whichare pivotally suspended at opposite ends from the upper and lower ends of the two levers 55. In each of the forms described above, the channel-shaped counterweight and the flanged top'of the rubbing shoe are nested compactly together so that the presence of the counterweight inan out of the way position between the body 10 and the rubbing shoe does not add appreciably to the over-all vertical height of the tool. Through the use of a single counterweight disposed close to the top of the shoe, it is possible to bring the centers of gravity of the two substantially into a common plane and thus achieve perfect counterbalancing of the shoe and vibrationless operating of the tool as a whole. At the same time, the shoe and the counterweight are guided effectually without the use of elongated way surfaces which are difficult to machine with the necessary accuracy and to lubricate properly in service.

If desired, the valve 30 controlling the operation of the motor 11 may be actuated by downward pressure applied to the part of the tool casing which is gripped and held by the operator in using the tool. For this purpose, the top 16 of the casing and its depending skirt 18 may be molded from flexible material such as rubber with a metallic liner 101 (Fig. 8) pivoted on pins 102 projecting from opposite sides of the tool body 10; These pinsare spaced from thevalve stem 82 which bears upwardly against the top of the casing 16. When this casing is gripped and downward pressure is applied to press the abrasive sheet against the work surface, the entire casing 16 is rocked downwardly thus depressing the stem 82 and opening the valve. The latter remains open and motor fluid is admitted to the motor as long'as downward pressure is'applied. When this pressure is released, the casing 16 moves upwardly under the action of the valve spring 103 and the valve becomes closed thereby terminating operation of the motor and the rubbing shoe.

This application is a continuation in part of my now abandoned applications Serial No. 139,930, filed January 21, 1950 and Serial No. 245,099, filed September 5, 1951.

I claim as my invention:

1. A rubbing machine having, in combination, a rigid body, a power actuated drive element mounted on said body and projecting downwardly therefrom, upright levers disposed on opposite sides of said body and pivoted intermediate their ends on the frame to swing about parallel horizontal axes, a rigid box-like frame defining an upwardly opening recess receiving said body and said levers and having a bottom wall forming a rubbing shoe,

means pivotally connecting the upper ends of said levers and the side walls of said body, a rigid counterweight disposed within said frame between said body and said shoe, means pivotally connecting said counterweight to the lower ends of said levers at points spaced along the length of said counterweight, and means connecting said projecting drive element and said counterweight and acting during operation of said drive element to reciprocate said counterweight back and forth.

2. A rubbing machine having, in combination, a rigid body, a power actuator on said body including a drive element projecting downwardly therefrom, upright levers disposed on opposite sides of said body and pivoted intermediate their ends on the body to swing about parallel horizontal axes, a rubbing shoe disposed below said body and having flanges upstanding rigidly from opposite ends alongside said levers, means pivotally connecting the upper ends of said levers and said flanges, a counterweight lying between said body and said shoe, means pivotally connecting said counterweight to the lower ends of said levers at points spaced along the length of said counterweight, and means connecting said projecting drive element and said counterweight and operating while said actuator is energized to reciprocate said counterweight back andforth.

' 3. A rubbing machine having, in combination, a rigid body, a drive shaft journaled in and projecting down-' wardly from said body, upright levers disposed on opposite sides of said body and pivoted intermediate their ends on the body to swing about parallel horizontal axes,

' a rubbing shoe disposed below said frame, means pivotally connecting the upper ends of said levers and opposite ends of said shoe, an elongated member disposed between said frame and said shoe, means pivotally connecting opposite ends of said member and the lower ends of said levers, and means including a crank connecting the projecting shaft end and said member and operating during rotation of the shaft to reciprocate the member back and forth.

7 4. A rubbing machine having, in combination, a body, a power actuator having a driven element extending below the body, upright levers fulcrumed intermediate their ends on horizontal pivots at opposite sides of said body, a counterweight disposed below said body, a pair of arms rigid with and upstanding from points spaced,

along the length of said counterweight and pivotally connected at their upper ends to the upper ends of said levers, -a rubbing pad disposed adjacent and below said counterweight, means pivotally connecting opposite ends of said pad to the lower ends of said levers, and means driven bysaid driven element to oscillate said levers back and forth and thereby reciprocate the counterweight and said pad in opposite directions.

5. A rubbing machine having, in combination, a body, a power actuator on said body, upright levers disposed on opposite sides of said body and pivoted thereon intermediate their ends to swingin a vertical plane, a counterweight disposed beneath said body and pivotally connected at points spaced along the length of said counterweight to one end of each of said levers, means connecting said actuator and said counterweight for reciprocating the latter during energization of the actuator, and a rubbing pad disposed adjacent and below said counterweight and pivotally connected at opposite ends to the other ends of said levers, said counterweight being sized to correspond to the weight of said pad.

6. A rubbing machine having, in combination, a rigid body, a rubbing shoe spaced below said body and supported thereby for reciprocation in a normally horizontal plane, a weight for counterbalancing said shoe during its reciprocation said counterweight being disposed above said shoe wtihin the space between the bottom of said body and the top of the shoe, a pair of levers fulcrumed intermediate theirends on said body and disposed in uprightposition on opposite sides thereof and above said shoe, means pivotally connecting opposite ends of each of said levers to said shoe and weight respectively, and power driven mechanism mounted on said body and operable to oscillate said levers back and forth in unison and thereby reciprocate said shoe and weight in opposite directions.

7. A rubbing machine having, in combination, a rigid body, two upright levers at opposite ends of said body pivoted thereon intermediate their endsto oscillate about laterally spaced parallel axes, a rubbing shoe spacedbelow said body and pivotally suspended from the upper ends of said levers, a counterweight disposed between said body and said shoe and pivotally suspended from the lower ends of said levers, and a power actuator mounted on said body and having a driven element extending outwardly from said body and connected to said levers for oscillation of the latter back and forth in unison.

8. A rubbing machine having, in combination, a rigid body, two upright levers at opposite ends of said body pivoted thereon intermediate their ends to oscillate about laterally spaced parallel axes, a rubbing shoe spaced below said body and pivotally suspended from one of the ends of said levers, a counterweight disposed between said body and said shoe and pivotally suspended from the other ends of said levers, a power actuator mounted on said body including a piston disposed about said countcrweight and reciprocable back and forth parallel to said shoe, and an upright stud having connections at opposite ends joining the stud with said piston and counterweight, one of said connections permitting of relative movement between the stud and the member joined thereto whereby to compensate for the difference in curvature between the paths of said pistonand said counterweight.

9. A rubbing machine having, in combination, a rigid body, a motor within said body including acylindcr and a piston reciprocable therein, upright levers disposed on opposite sides of said body and pivoted intermediate their ends on the body to swing about axes paralleling said cylinders, 21 counterweight disposed beneath said body and pivotally connected at points spaced along the length of said counterweight to the ends of said levers, a stud joined at opposite ends to said counterweight and piston and projecting through the side of said cylinder, a rubbing shoe disposed adjacent and below said counterweight, and means pivotally connecting opposite ends of said counterweight to the other, ends of said levers.

10. A rubbing machine having, in combination, a rigid body, a rubbing shoe having a rubbing surface spaced below the lowermost portion of said body, a rigid counterweight for counterbalancing said shoe during its reciprocation and disposed adjacent but above said rubbing surface and positioned within said shoe, means on said body mounting said counterweight and said shoe beneath the longitudinal center of said body for reciprocation in a normally horizontal plane and in opposite directions and movement of their respective centers of gravity substantially in a common, normally horizontal plane spaced above said rubbing surface, and power driven mechanism mounted on said body and operable to reciprocate said shoe and counterweight in unison and in opposite directions.

References Cited in the file of this patent UNITED STATES PATENTS 1,699,029 Scott Jan. 15, 1929 1,957,790 Mavis May 8, 1934 2,345,383 Curtis Mar. 28, 1944 2,437,152 Burleigh Mar. 2, 1948 2,517,548 Dobson Aug. 8, 1950 FOREIGN PATENTS 668,774 Great Britain Mar. 19, 1952 

